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Registered 2000 SLK230
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Discussion Starter #1
For the past month, I have endured a rough running engine due to cylinders 1 and 4 occasionally not firing. Sometimes, I can turn the ignition off and restart the engine to clear the problem.

So far I have: Ran Injector cleaner through the last two tanks of gas, cleaned the MAF ( I replaced 1 year ago), replaced the fuel pressure regulator, fuel filter, fuel pump and Throttle Position sensor. 1 year ago, I replaced the sparkplugs, coils and both O2 sensors. I have disconnected the battery twice for over an hour each time.

What could it be?

I get 5 codes indicating O2 failure, misfires on cylinders 1 and 4.

I'm thinking I may have to replace the ECU.

You suggestions are greatly appreciated.

Pat
 

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Premium Member
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Where did you get your new MAF?
 

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Registered 2000 SLK230
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34 Posts
Discussion Starter #3
I bought the MAF on the internet but I do not remember what brand. Today, the car barely made it to/from work. I figured it was dead. When I got home, I cleaned the sparkplugs and swapped the coil packs. Cylinder 1 and 4 are misfiring and have a common coil. I cleaned the plugs, too. I reassembled the plugs and wires and the engine ran perfect. Tomorrow, if I get a misfire, I hope it is on cylinder 2 and 3 thus proving I have a bad coil pack.

I am still open to suggestions.
 

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Registered 2000 SLK230
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34 Posts
Discussion Starter #4
it could be the wires are loose or corroded going to the coil pack for #1 and #4. I don't know....I'm just an aircraft/helicopter mechanic. If I knew what I was doing, I'd be working on cars. :)

Pat
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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98,080 Posts
Pat, until other r170 experts chime in, I recall someone saying some mafs bought on the internet are bad

from jfr:
i should say take a real new MAF from MB.
it's not rare to get bad MAF from internet.
unplug the MAF and see if the car doesn't change . . . that's mean the MAF is inefficient.

from efair:
Agreed, if you have your old MAF still put it back in and see if anything changes. P0100 means MAF failure.

A minor vacuum leak wouldn't account for not making it up hills -- but an ME that's decided to ignore the MAF would.

from livefreeordie:

You have to be careful with the ebay MAF there have been reports of them not working. If your going to buy a new one goto a good parts store or auto supply warehouse.
 

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1,613 Posts
I bought the MAF on the internet but I do not remember what brand. Today, the car barely made it to/from work. I figured it was dead. When I got home, I cleaned the sparkplugs and swapped the coil packs. Cylinder 1 and 4 are misfiring and have a common coil. I cleaned the plugs, too. I reassembled the plugs and wires and the engine ran perfect. Tomorrow, if I get a misfire, I hope it is on cylinder 2 and 3 thus proving I have a bad coil pack.

I am still open to suggestions.
Sounds like ouch... German cars are very sensitive to aftermarket MAFs.
OEMs are calibrated for your specific car's ECU.
Yes, OEM ones are expensive ($300-$400) but ECU doesn't like them =(
Last resort would be aftermarket Bosch MAFs for cars. Any other I wouldn't dare.
 

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what kind of plugs are they? Might want to check into the CPS as well
Livefreeordie has a good point. Check the Crankshaft Positioning Sensor!
Does your look like mine did?

Then, chances are it's leaking. It's a famous recall so no worries!
Also, spark plugs. OEM ones should be NGK's or at least aftermarket Bosch.
 

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Premium Member 2002 SLK230K
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17,144 Posts
All that gunk is from the cam shaft position sensor. I could be wrong but i think the recall is over for that part. The CPS (crank shaft sensor) is located on the driver side below the throttle body close to the bell housing. I had missfire problems when ever i got a heavy foot, a new cps solved the problem. If your using those fancey plugs get rid of them and stick with OEM type.
 

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Registered 2000 SLK230
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34 Posts
Discussion Starter #10
Well, I think, actually I'm sure, I have solve the problem. Yesterday, I swapped the ignition coils and today the problem followed. Yesterday, cylinder 1 and 4 misfired. Today cylinder 2 and 3 are misfiring. To me, that confirms a bad coil.

Yesterday, I removed the air hose to the MAF and that triggered a code.

I just love my car. Not since my '73 Datsun 240Z have I enjoyed a car so much.

MY next problem is I need to locate an actuating cylinder for the mechanical hard top. It is the big cylinder and I do not think it is the rebuildable one. What is a good source for them?

Thanks a million.

Pat
 

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Registered
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1,613 Posts
Well, I think, actually I'm sure, I have solve the problem. Yesterday, I swapped the ignition coils and today the problem followed. Yesterday, cylinder 1 and 4 misfired. Today cylinder 2 and 3 are misfiring. To me, that confirms a bad coil.

Yesterday, I removed the air hose to the MAF and that triggered a code.

I just love my car. Not since my '73 Datsun 240Z have I enjoyed a car so much.

MY next problem is I need to locate an actuating cylinder for the mechanical hard top. It is the big cylinder and I do not think it is the rebuildable one. What is a good source for them?

Thanks a million.

Pat
Great you found the culprit! Then all you need is new coil packs. Don't go cheap on them. I'd say go OEM or Bosch.
Are you talking about the top locking cylinder? If so, it's under the headliner. The DIY section is full of info about the roof cylinders =)
Never heard if someone rebuilt one but I think Ebay is the way to go unless you want a new one.
 

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Premium Member 2014 SLK55 AMG
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1,669 Posts
After 2 dodgy ebay MAF's on r170's I learned a lesson.

If you put in a new part and the problem changes then try reinstall the original part ( unless its very obviously broken ) .

My 320 'ran a bit lumpy' so i replaced the MAF with an ebay part ..... Twice. The problem got vastly worse. First getting very bad when the engine was hot and then developing a complete breakdown at 5000 rpm.

Back to the original MAF and live with the lumpiness!

If i'd kept the car the only option would have been an original part I think.
 
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